This invention relates to an exterior rear view mirror for a vehicle of the type in which the orientation of a reflective member is adjustable relative to the vehicle. The invention is particularly, but not exclusively, applicable to mirrors of the above type in which the adjustment is performed using an electrically powered system.
Legal regulations specify that a vehicle exterior mirror must provide a driver of the vehicle with a prescribed field of view. To facilitate adjustment of the field of view to suit a particular driver, it has become customary to provide exterior mirrors with means for adjusting the orientation of the reflective member thereof from within the vehicle. Where such adjustment is performed using an electrically powered mechanism, it has been customary to provide two electric motors, one for adjusting the orientation about a vertical axis and the other for adjusting the orientation about a horizontal axis.
In a motor car, the horizontal position of a driver""s eyes in relation to a vehicle exterior mirror is determined principally by the length of the driver""s legs since this is the factor affecting how far back the driver chooses to push his seat. The vertical distance between the mirror and the driver""s eyes is determined by the length of the driver""s body since this determines the height of the his eyes above his seat. Since, in the human body, leg length is not directly related to body length, there is a significant spread of possible positions for the driver""s eyes. It has been found that, for the 95th percentile of the human population, these possible positions are within a zone which is of generally elliptical shape in the vertical plane. When allowance is made for the horizontal separation between the drive""s two eyes and for the effect of the driver turning his head, the distribution is also somewhat elliptical in the horizontal direction.
To facilitate vehicle design, the concept of the driver""s xe2x80x9ceyellipsexe2x80x9d has been devised to specify the overall distribution of eye position resulting from the above variations. This concept is defined in the 1988 SAE Handbook, Volume 4 xe2x80x9cOn-Highway Vehicles and Off-Highway Machineryxe2x80x9d, Recommended Practice SAE J1050a xe2x80x9cDescribing and Measuring the Driver""s Field of Viewxe2x80x9d, published by the Society of Automotive Engineers, Inc. It is common practice, for a motor vehicle manufacturer to use this practice to establish the location and dimensions of the eyellipse of a vehicle in relation to the required position for an exterior mirror and to supply this information to the mirror designer.
It should be understood that the term xe2x80x9ceyellipsexe2x80x9d does not mean that the shapes so described are necessarily true mathematical ellipses but merely that they are of generally similar shape to true mathematical ellipses.
According to a first aspect of the invention, an exterior rear view mirror for a vehicle comprises pivotal coupling means, a reflective member mounted on said pivotal coupling means which allows angular movement of the reflective member about a pivot axis perpendicular to a plane containing both a first line and a second line, wherein the first line bisects the angle between an incident ray and a reflection of said incident ray extending to a first end of the major axis of a vertical section through the eyellipse, and the second line bisects the angle between said incident ray and a reflection of said incident ray extending to a second end of said major axis.
This avoids the need to make provision for angular movement of the reflective member about a second pivot axis perpendicular to the first-mentioned pivot axis.
Preferably, the incident ray extends from the bottom corner of the required field of view closest to the vehicle.
The reflective member may be pivotally mounted in a mirror case for angular movement relative thereto about said single pivot axis. Alternatively, the reflective member may be rigidly mounted in the mirror case which is itself pivotally mounted on a bracket for angular movement relative thereto about said single pivot axis, in which event said axis also serves as the axis about which the mirror case can be displaced in the event that it is subject to impact.
According to a second aspect of the invention, an exterior rear view mirror comprises a mirror case, a reflective member, pivotal coupling means mounting the reflective member in the mirror case so as to allowing angular movement of the reflective member relative to the case, drive means coupled to the reflective member at a first location spaced from the first axis and arranged to cause angular movement of the reflective member about the first axis, and stop means arranged to abut against the reflective member at a second location spaced from both the first location and the first axis, the pivotal coupling means being resiliently coupled to the case so as to allow angular movement of the reflective member about a second axis inclined to the first axis during continued operation of the drive means following abutment of the reflective member against the stop means.
This avoids the need for separate drive means for tilting the reflective member downwardly when it is desired to provide a view of the ground immediately adjacent to the rear of the vehicle.
Preferably, the pivotal coupling means comprises a first pivot joint rigidly secured to the mirror case and a second pivot joint resiliently secured to the mirror case.
According to a third aspect of the invention, an exterior rear view mirror for a vehicle, comprises a bracket adapted to be mounted on a vehicle body, a mirror case mounted on the bracket for angular movement relative thereto, a reflective member mounted in the mirror case, an electric motor in the mirror case, and a worm wheel driven by said electric motor, the worm wheel being journaled in sprung bearings so as to be resiliently biased into engagement with a pinion which is coupled to the bracket.